This invention pertains to a tester contact for testing electrical contacts, and in particular to a tester contact which reliably provides for efficient current sourcing and voltage sensing.
Currently, test equipment for multi-function switches and ignition switches are provided with a connector having Pogo.RTM. contacts (PYLON Company, Inc., Attleboro Fails, Mass.) or custom built test contacts. Referring to FIG. 1, a Pogo.RTM. contact 10 generally consists of a conductive tubular housing 12 with a single cylindrical electrical contact 14 which is slidably mounted within the housing. Furthermore, the first end 16 of the electrical contact 14 extends from the tubular housing 12 and the second end 18 of the electrical contact is acted upon by a spring 20 and bail 22 assembly mounted within the tubular housing.
Electrical testing is performed by pressing the first end 16 of the electrical contact 14 against an electrical test point on the switch to be tested (test point and switch not depicted in FIG. 1). However, the amount of actual pressure applied by the Pogo.RTM. contact 10 is determined by how much force the spring 20 and bail 22 assembly exerts in pushing the first end 16 of the electrical contact 14 against the test point of the switch. Furthermore, the pushing of the electrical contact 14 against the test point results in the need to firmly hold the switch in place so that it will not move away from the Pogo.RTM. contact 10.
Problems also occur with the utilization of the Pogo.RTM. contact 10 whenever foreign material is present between the first end 16 of the electrical contact 14 and the test point, or if any foreign material is present within the Pogo.RTM. contact itself. Any foreign material which is not removed before testing may prevent or result in inaccurate test results.
Likewise, the single electrical test contact 14 provided by the Pogo.RTM. contact 10 will prevent separate current sourcing and voltage sensing of the test point. Therefore, the use of a single electrical contact 14 will result in a greater voltage sense error as the level of current being sourced is increased.
Turning to FIG. 2, a custom built test contact assembly 24 is depicted. The custom contact assembly 24 generally consists of two conductive beams 26,26, made of a conductive metallic material, which are surrounded by two rubber bands 28,28 located adjacent to the ends of the beams. In addition, an insulator plate 30 is sandwiched between the conductive beams 26,26 and thus allows for separate current sourcing and voltage sensing by the beams.
Each beam 26 of the custom contact assembly 24 has a first end 32 and a second end 34. As shown by the top view of the custom contact assembly depicted in FIG. 3, the cross section of each beam 26 has a flat side 36 and a rounded side 38 which results in the beam being generally D-shape in cross section. The flat side 36 of each beam 26 adjoins the insulator plate 30 so that the insulator plate is sandwiched between both of the beams. However, referring back to FIG. 2, the insulator plate 30 does not extend the full length of the beams 26,26 which results in a slot 40 being provided between the beams on the first end 32. In addition, the first end 32 of each beam 26 is tapered 41 between the flat portion 36 and the first end 32 in order to facilitate the insertion of the object under test between the beams.
Turning back to FIG. 3, as stated previously, two rubber bands 28 extend around the rounded side 38 of each beam 26,26 (only one band is shown). The bands are located on each end of the beams and the insulator plate 30. The bands provide a constant force to hold the insulator plate 30 between the beams 26,26.
When a test item is to be place in the slot 40 between the beams 26,26 in FIG. 2, the beams will separate. The separation of the beams is made possible by the resiliency of the bands 28,28 and the limited flexibility of the beams 26,26. However, the design of the test contact assembly 24 has several significant limitations. First, the custom contact assembly 24 is very time consuming to build and repair. Second, after repeated expansion and contraction during the insertion and removal of test items between the contact beams 26,26, the bands 28,28 will become fatigued and thus will need to be replaced. Third, when an item is inserted in the slot 40 between the beams 26,26, the electrical contact area is limited to the narrow area on the test item being pinched by the two beams. The last limitation cannot be overcome by simply making each of the beams flat because they would quickly cut into the bands with their sharp edges.
In view of the above, it is an object of the present invention to provide for separate current sourcing and voltage sensing.
A further object of the invention is to provide a contact which wipes foreign matter away from the test point.
Also an object of the invention is to provide a reliable electrical connection between the tester contact and the item under test.
An additional object of the invention is to provide a contact which holds the test item.
Another object of the invention is to provide a contact which is easily maintained.
It is also an object of the invention to provide a contact which is easy to manufacture.
An additional object of the invention is to provide a reliable contact.